1. Field of the Invention
The present invention relates to a dimming structure for an image display device in which light and darkness around an image outputted through the display device is controlled to impart vividness to the image, and more particularly, a dimming structure for an image display device which further includes a contrast panel for altering contrast differences in a portion around the image outputted in order to produce dimming effects on the image smaller than a light emitting lamp.
2. Description of the Related Art
With various display devices popularized and commercialized, there has been considerable technological advancement in color reproducibility and power consumption reduction. Lately, a liquid crystal display (LCD) has been noticeably adopted for the display devices.
In general, the LCD device is constructed of a display panel for displaying an image through light and a backlight unit for generating light. The backlight unit is designed mainly to supply light evenly to an effective display area where the image of the display panel is displayed.
Recently, in an effort to develop the LCD device, diverse approaches have been deployed to output a more vivid and life-like image, i.e., an image with visual depth to enhance display quality. To impart vividness and visual depth to the image, chiefly, brightness has been partially boosted to increase a contrast ratio. Moreover, the LCD devices featuring this function have been put on the market.
A conventional LCD device will be explained in detail hereunder with reference to the accompanying drawings.
FIG. 1 sequentially illustrates operation of the conventional LCD device.
As shown in FIG. 1, the conventional LCD device 1 includes a backlight unit 2 provided with a plurality of light sources 20 and a display panel 3 for displaying an image 30. Here, each of the light sources 20 is shaped as a bar.
According to an example shown in FIG. 1, as an image such as light moves in a dark place, a peripheral portion of the image 30 also is moderately brightened. When the image 30 is displayed in a portion of the display panel 3 as in step (a), one of the light sources corresponding to the image 30, i.e., a third light source is a high brightness light source 22. Also, left and right ones of the light sources 20 about the high brightness light source 22, i.e., the second and fourth light sources are low brightness light sources 24. The rest of the light sources excluding the high-brightness and low-brightness light sources 22 and 24 are off light sources 26 that do not emit light.
In step (b) where the image 30 is shifted to the right by a half width of the light source 20 from step (a), a third light source and the fourth light source between which the image 30 is straddled are the high-brightness light source 22. Moreover, left and right ones of the light sources 20 about the high-brightness light source 22, i.e., the second light source and a fifth light source are the low-brightness light sources 24. The rest of the light sources excluding the high-brightness and low-brightness light sources 22 and 24 are the off light sources 26 that do not emit light.
Further, in step (c) where the image 30 is shifted to the right by a half width of the light source 20 from step (b), the image 30 corresponds to only the fourth light source. Thus, the fourth light source is the high-brightness light source 22 and left and right ones of the light sources 20 about the high-brightness light source 22, i.e., the third and fifth light sources are the low-brightness light sources 24. The rest of the light sources excluding the high-brightness and low-brightness light sources 22 and 24 are the off light sources 26 that do not emit light.
In this fashion, each of the light sources 20 is varied in light emitting amount according to location of the image 30 to enhance life-likeness of the image 30. That is, the image 30 is displayed bright, the peripheral portion thereof is displayed moderately bright, i.e., dim, and a portion located at a predetermined distance from the image is displayed dark.
Here, in a case where the light source 20 has a width very smaller than that of the image 30, the dim portion is displayed more clearly, thus more assuring life-likeness. Meanwhile, in a case where the light source has a width similar to or greater than that of the image 30, the dim portion is not displayed clearly, thus rendered less life-like. That is, in a case where the image 30 is positioned to correspond to only one of the light sources 20 as in step (a), left and right portions from the image 30 correspond to only the low-brightness light sources 24, thus making the left and right portions from the image 30 evenly bright. On the other hand, in a case where the image 30 straddles between the two light sources 20 as in step (b), the left and right portions from the image 30 correspond to the high-brightness light source 22 and the low-brightness light source 24, respectively. This leads to differences in brightness between the left and right portions from the image 30, thereby undermining vividness.
In addition, as shown in FIG. 1, when the light sources 20 are respectively shaped as a bar, some portions of the panel 3 positioned above and under the image 30 correspond to the area of the high-brightness light source 22, thus looking brighter than other portions of the panel 3 positioned in the left and right from the image 30.
FIG. 2 sequentially illustrates operation of another conventional LCD device.
To solve the problem of the LCD device shown in FIG. 1, the LCD device 1 has been suggested, in which a plurality of small LEDs 10 are densely arranged thereon as shown in FIG. 2.
When the LCD device 10 of FIG. 2 displays an image such as bright light, some portions of the LEDs corresponding to the image are a high-brightness LED 12. Some other LEDs arranged adjacent to the high-brightness LED 12 are a low-brightness LED 14 and the rest of the LEDs are an off LED 16, thereby giving visual depth to the image.
As described above, the LCD device 1 having the small LEDs arranged thereon more densely can display a smaller image by operating the LEDs positioned in the left and right sides and the upper and lower sides individually. Accordingly, the LCD device 1 can more clearly display a peripheral portion of the image, i.e., where light is emitted dimly, thereby leading to a more life-like image.
However, the conventional LCD device shown in FIG. 2 requires a plurality of LEDs to be disposed thereon, thus increasing manufacturing costs and consuming great power. Also, each of the LEDs releases considerable heat amount, thus necessitating a separate heat releasing structure. Moreover, in the conventional LCD device, each of the LEDs should be respectively wired to be controlled independently. This complicates internal configuration of the device and requires a significant number of circuit structures.